1. Field of the Invention
The present invention is directed to a position transmitter (detector) for acquiring the position of a light beam. The term "light beam" is used herein in the broadest sense and refers to an electromagnetic emission beyond the visible range, or particles as well, cause the generation of a current from a transducer.
2. Description of the Prior Art
Position transmitters are known in the art composed of two electrodes each formed by a photodiode, the photodiodes being disposed perpendicularly to each other. Such detectors are employed whenever it is useful to monitor the variation of the relative positions the light beam and the position transmitter.
Thus, position transmitters are employed as goniometers (angle measuring units) when the light beam does not vary in position and the position transmitter is arranged, for example, on a cylindrical exterior surface of a rotating subject. Position transmitters also can be employed for the adjustment of an apparatus, whereby the transmitter itself is rigidly connected to one apparatus part and a reference light beam, for example a laser beam, that serves the purpose of adjustment is incident on the surface of the position transmitter.
Position transmitters are known that are essentially composed of a uniform, photosensitive detector surface and a signal read-out and evaluation circuit. Currents from the point of incidence of a light beam on the uniform detector surface to two edges of the detector surface that reside perpendicularly to one another are sampled with this circuit and the position of the point of incidence of the light beam on the detector is calculated therefrom. Inhomogeneities in the photosensitivity, or in the values of resistance of the detector surface, falsify the result of the position identification. Stray light or daylight incident onto the detector surface also falsify the result, since the currents are then not exclusively caused by the incidence of the light beam to be measured on the detector surface.